公开(公告)号：KR810000752B1

公开(公告)日：1981-06-27

申请号：KR770000032

申请日：1977-01-10

Applicant: MOTOROLA INC

Inventor： CHARLES WILLIAM BETHARDS

IPC: H03L5/00

Abstract: An amplitude modulated transmitter includes an audio amplifier which modulates an RF amplifier and carrier. Fluctuations of DC bias to the RF amp. vary the modulation index of the trasmitted signal. To minimize DC bias affects on the modulation index, the audio compressor senses both audio signal level and DC bias level and controls audio signal compression to maintain the desired percent modulation. Compression is effected by changing the bias on a semiconductor device (52) which attenuates audio signals at the input of a fixed gain audio amplifier(64). A feedback path around the audio amplifier senses both DC voltage and audio signal level and produces an control signal to bias the semiconductor device (52).